Correct Gauge Wire For Parallel Dual Battery

[RhyssM]

First Install with a Parallel circuit or this distance.

Connecting 2x 12V 90ah AGM batteries in parallel and the cable length with roughly be 2 meters in length. Putting the batteries any closer is not an option due to space restrictions. 20-30amps is roughly what will be drawn at one given time in the circuit for the time being.

What size cable/amp is best suited?

Much appreciated

 

[Zerax]

Have you tried an online cable sizing calculator ? There are many of them out there... such as this one:

DC Cable Size Calculator | Fabhabs

Easy calculator to size DC cables based on their length, current, and citcuit voltage. Ideal for 12V and 24V systems such as campers, van conversions, and solar projects. Need to know how thick a cable needs to be for a solar panel, fridge, battery, or motor? Use this calculator to find out.

www.fabhabs.com

But... remember that with DC, you want the total length of +ve & -ve added together... and... if I were you... treat the result given from the calculator as an absolute minimum... go as big as you can afford/install/manage etc. Also, make sure that you have proper crimped terminal lugs at the end of each cable.

 

[James]

I would be working with 25mm trirated or welding cable as a minimum.
It will help avoid volt drop.
But more importantly, 2 batteries of that size in parallel will provide several hundred amps if there was ever a short circuit.

 

[DPG]

Hopefully there is suitable fusing close to each battery!

 

[ruston]

Hopefully there is suitable fusing close to each battery!

Sadly usually the wiring harness.

 

[Zerax]

I'd use cube fuses on the battery terminals...

 

[DPG]

I'd use cube fuses on the battery terminals...

Sounds a good idea. Closer to the battery the better eh.

 

[Lucien Nunes]

Other than the maximum load current to be drawn, the most important criterion for battery cable size is usually what kind of charger is being connected and where, because voltage drop during charging is extremely detrimental to charging performance and could result in one battery receiving less charge than the other. As above, with batteries of that size, although the length is short there's no excuse for using less than say 25mm² / #3 AWG copper. This will ensure that at any charge rate the batteries can handle the voltage drop will not be an issue. It will also probably survive a momentary short-circuit, but fusing at the posts e.g. with the cube fuses mentioned is a very good way to protect against burnout. Additional fusing might be needed to protect the wiring downstream.

remember that with DC, you want the total length of +ve & -ve added together.

Perhaps I've missed the point but I am not sure how that differs from AC other than the names of the conductors.

 

[RhyssM]

I'd use cube fuses on the battery terminals...

Definitely will use these awesome thought